Corrosion of copper conductors poses a severe threat to water-cooled generators. It leads to an increase in copper ion concentration within the cooling water, which raises the water's electrical conductivity and elevates the risk of current leakage. Furthermore, corrosion products can accumulate inside the hollow copper conductors, obstructing the cooling channels; this causes a sharp rise in conductor temperature, potentially leading to insulation failure. Additionally, the corrosion of hollow copper conductors can increase the hydrogen content in the stator cooling water, which may trigger an unscheduled unit shutdown. A notable example occurred at the No. 2 generator of Changchun Second Thermal Power Co., Ltd., where an emergency shutdown was necessitated after the hydrogen content in the internal cooling water tank exceeded 8%.
The corrosion of hollow copper conductors is primarily linked to the accumulation of water inside them and their exposure to atmospheric components such as carbon dioxide and oxygen.
To prevent corrosion, measures such as purging with dry air, dehumidification via vacuum pumps, and nitrogen blanketing should be implemented to avoid internal water accumulation and contact with the atmosphere.
As generator capacities increase, the demand for exceptionally long, seamless hollow conductors has introduced new technical challenges. For instance, the hollow conductors required for a 700 MW dual-water-cooled generator can weigh up to 273 kg per individual piece-exceeding the production capacity of existing supplier equipment-while also requiring wall-thickness tolerances to be maintained within ±0.10 mm. These challenges are addressed by optimizing die design and refining core manufacturing processes, such as extrusion and cold rolling.
To ensure the reliability of hollow conductors, they must undergo rigorous inspection. This includes examining the internal and external surfaces, verifying dimensions, and testing mechanical and electrical properties. Depending on the purchaser's requirements, additional evaluations-such as hydrostatic pressure testing, eddy-current testing, and oxygen content analysis-are also conducted.
